Glass colorant compositions

ABSTRACT

COLORANT-ENRICHED FRIT GLASS COMPOSITIONS OF THE FOLLOWING INGREDIENTS ARE DISCLOSED TOGETHER WITH METHODS OF PRODUCING COLORED GLASSES USING SAME:   PERCENT BY WEIGHT   COMPOSI- COMPOSI- COMPOSITION 1 TION 2 TION 3   INGREDIENTS: SIO2 15-50 CR2O3 2-10 2-10 R2O 23-46 NA2O X 21-30 10-40 K2O (1) 0-7 B2O3 10. 5-47 49-70 35-70 R2O + B2O3 44-74 FE2O3 O-10 COO O-8 O-43 MNO O-18 O-23 PBO, BAO AND ZNO O-15 NIO 2O-18 FE2O3 2O-18 ZNO 2O-43 CUO 2O-28   1 LESS THAN 25% X. 2 AT LEAST 2%.

Feb. 9, 1971 E. c. HAGEDQRN ETAL 3,561,985

` A@mss coLoRANT COMPOSITIONS Filed Sept. 16, 1966 United States Patent O U.S. Cl. 106-54 5 Claims ABSTRACT F THE DISCLOSURE Colorant-enriched frit glass compositions of the following ingredients are disclosed together with methods of producing colored glasses using same:

Percent by weight Composi- Compositron 1 tlon 2 Ingredients: SiO

i 1 Less than 25% X.

2 At least 2%.

The present application is a continuation-in-part of applicants copending application Ser. No. 285,088, filed June 3, 1963, and now abandoned in favor of the present application.

This invention relates to a colorant-enriched glass suitable for use in coloring a base glass and, more particularly, to a colorant-enriched glass frit having a high concentration of chromium oxides.

Colorant-enriched glasses suitable for forehearth addition, in frit or molten form, to a colorless base glass to form a composite color glass are known, as are colorant-enriched glass frits containing chromium oxides. A number of patents disclosing such frits for making colored glasses and ultraviolet absorbent glasses, the latter having a specific concentration of chromium oxide wherein the chromium is hexavalent, have been issued to the assignee of the present application.

Colorant-enriched glass compositions are disclosed in Hagedorn Pat. 3,024,121, granted Mar. 6, 1962; Swain Pat. 2,923,636 granted Feb. 2, 1960; and Babcock Pat. 3,024,120, granted Mar. 6, 1962.

In general, however, such frits as disclosed in these patents have high melting temperatures and/or relatively high viscosities when molten, so as to present certain diiculties and disadvantages in the processes for forming colored glasses. These include higher costs due to the need of increased temperatures to melt the frit, volatilization and consequent loss of certain of the ingredients in the glass because of the high temperature, increased tendency for the chromium and other colorant oxides at high percentages to crystallize and form inclusions in the resulting colored glass, and diculty in thoroughly dispersing the molten frit throughout the molten base glass due to the relatively high viscosity of the molten ice frit. Solution and devitriiication problems are greatly increased, especially in the production of highly reduced chromium frits.

Accordingly, it is an object of the present invention to provide a colorant-enriched glass composition suitable for use in coloring a base glass, and which is free of the aforementioned dillculties and disadvantages.

It is a further object of the present invention to provide a family of colorant-enriched glasses suitable for use in coloring a base glass, which glasses have low melting temperatures, low viscosities, and are readily miscible with colorless molten base glasses to form uniformly colored glasses.

It is another object of the present invention to provide glasses having a high concentration of chromium oxides, i.e., from about 2 to about 10% or more, and which, when added in frit or molten form to a colorless molten base glass, impart a yellow-green, green, or blue color to the base glasses, and which, if desired, will also im part the ability to absorb substantially all ultraviolet radiation to which it may be subjected.

In attaining the objects of the present invention, one feature resides in maintaining the silica content of the colorant-enriched glass at a low level while maintaining a high concentration of a mixture of alkali metal oxides and B203 wherein the total of the alkali metal oxides and B203 is from 44% to 74% 'by weight of the colorant-enriched glass, which glass has a lower viscosity and is more readily miscible with the molten base glass than conventional high-silica-coloring frits.

Another feature of the invention resides in forming a colorant-enriched, silica-free glass having a critical content of alkali metal oxides and B203, which glass can be formed at a temperature as low as from about 1200"- 1400 F., and which has a low viscosity relative to known highly colorant-enriched glass frits, so that it can readily be added to and mixed with a molten base glass at the forehearth to produce a uniform color in the resulting glass article.

Other objects, featuses, and advantages of this invention will become more apparent from a reading of the following disclosure.

Glass frits having the capacity to dissolve significant amounts of various colorant oxides such as chromium, cobalt, nickel, iron, zinc, manganese and copper, While maintaining a low viscosity have many advantages over frits of the prior art, including (l) making possible and practicable the formation of high-chromium colored glasses such as emerald green, Ultrasorb emerald green, and champagne green; (2) reducing the amount of frit necessary to impart the desired colors; (3) improving the mixing in the forehearth due to lower viscosity and surface tension; (4) reducing the temperature necessary for melting the frit; and (5) making possible molten frit additions from small electric furnaces above the forehearths'.

It has been found that highly colorant-enriched glass compositions having the following essential ingredients are suitable for addition as frits or in a molten state, to a molten colorless base glass at the forehearth:

In the above list, R20 represents a mixture of Na20 and K20, with the latter being present in an amount less than 25% by weight of the former. The foregoing compositions can accommodate, without recrystallization, more than 2% by weight of the various colorant oxides. Thus,

3 the compositions of the invention contain more than 2% chromium oxides in the vitreous state.

When colorant-enriched glass frits made in accordance with this invention are to be stored for any length of time prior to use, it has been found that the presence of A1203 in the frit composition increases the chemical durability of the frit while simultaneously preventing the agglomeration of the frit particles. When forehearth frit additions are made, it is important that the frit particles be free? flowing and readily dispersible throughout the molten base glass. The presence of a sufficient amount of alumina, up to about l0 percent by weight of the glass frit composition, and preferably from 0.5 to 7%, prevents the frit particles from adhering to each other during storage.

While the oxides of chromium are present, other metal oxides can also be present in the glass frit composition in the following amounts without materially affecting the ability of the frit to hold a high chromium content, it being understood that the maximum amount of each should not `be present in the composition at the same time.

10 essential ingredients:

Ingredients: Percent by weight Na2O 21-30 K2O 0-7 B202 49-70 CI`203 OVCI' 2 F6203 The total amount of Cr203 in the vitreous state in the composition will vary from above 2 to about 10% or more. Minor amounts of the following oxides may also be present without materially ifecting the low melting temperature or relatively low viscosity of the above composition.

Percent by weight CoO 0-8 MnO 0-18 TABLE IIL-COLORANT-ENRICHED GLASSES (PERCENT BY WEIGHT) Ingredients:

The following are illustrative of frits coming within the scope of this invention: 45

TABLE L-COLORANT-ENRICHED GLASSES (PERCENT BY WEIGHT) (B) (C) (D) (E) (F) (G) (H) (I) (I) (K) 13.17 32.54 23.51 40.01 22.37 41.39 23.50 42.21 22.20 30.61 5.36 5.35 5.35 6.59 6.30 3.32 7.10 4.62 8.32 6.65 33.53 44.41 43.75 26.36 31.34 30.65 36.05 29.17 40.35 20.42 1.66 1.66 1.66 1.10 2.15 2.53 4.39 3.53 2.58 4.12 37.36 12.47 22.09 21.65 21.36 11.64 22.01 11.0 20.63 30.16 0.93 0.93 0.93 1.15 1.20 1.44 6.61 3.59 1.44 0.62 0.61 0.61 0.76 0.30 0.97 0.97 1. 76 1. 76 1. 76 2. 09 2. 1s 2. 53 o. 03 0. o3 2. 64 0.20 0.23 0.30 0.37 0.44 0.25 0.22 0.37 10.3.,` Pbo 5.03

The frits of Table I were prepared by melting the following raw batch materials and quenching on a steel 60 plate.

TABLE Il'.-COMPOSITION (PARTS BY WEIGHT) Raw materials:

t and 42. 1 20 0 36. 2 25. l5 2-. 1 19. 6 Soda ash 30.8 64 8 75.3 66. 9 30. 81 33. 7 Borax (dehydrated) 34. 1 20. 8 36.8 34. 1 27. 6 Iron chromite 5. 78 6 94 6. 94 6. 94 8. 12 6. 95 Potassium dichromate 4.83 5 80 5.80 5. 80 6. 76 5.79 Cobalt oxide (C0304) 0.32 0.32 0.32 0.32 0.32

Boric acid (anhydride) Calcium carbonate..

Nepheline Lead oxide (Pb304) M1102 yenite..

Again, it is to be understood that the maximum amounts of these added oxides are not to be present at one time. If one wanted; one could add up to about or more SiO2 to the aforesaid listed compositions as long as the ability of the particular composition to accommodate the desired amount of chromium oxide in the vitreous state was not materially affected.

In practicing the present invention, it is often advantageous to adjust the density of the frit glass to approach the density of the base glass in the interest of efficiency in mixing. We have found that this can be accomplished by incorporating the oxides of lead, barium, zinc, and mixtures thereof into the sodium borate frit composition. For instance, ordinary sodalime base glass has a density of about 2.5 gm./cc., while certain of the sodium borate frits of the invention have a density of about 2.4 gm./ cc. It has been found that the density of the frit can be tailored to achieve optimum mixing by incorporating up to of the combined oxides of ZnO, BaO and PbO into the frit batch. In the ideal situation, the density of the frit will be numerically equal to or greater than the density of the base glass.

TABLE III(a).-COLORANT-ENRICHED GLASSES (PERCENT BY WEIGHT) CuO Densityfgm/ce 2. 376 2. 778 2. 476

In the absence of the oxides of chromium, the alkali borate system of the invention is an excellent vehicle for the forehearth addition of other colorant metal oxides to a molten base glass. We have found that these alkali borate glasses, particularly the sodium borate glasses, are capable of dissolving unexpected amounts of the oxides of nickel, iron, manganese, cobalt, zinc, copper and mixtures thereof. It will be understood that the maximum solubility of any particular colorant oxide occurs when all other colorants are absent, even though signicant amounts of the above mentioned oxides can be dissolved together in a single frit composition.

Usually these frits are within the composition range:

Total Manganese as MnO CoO ZnO CuO (wherein the combined colorant oxide content is at least 2% by weight).

6 It is usually preferred that at least 5% of the particular colorant oxide be present in the frit to minimize the amount of frit to be added to achieve the desired degree of coloration in the composite glass. 5 In one embodiment of the present invention a single colorant oxide from the above list is present in the alkali borate frit. The amount of colorants will be at least 2% by weight and preferably 5% by weight of the frit composition. The maximum amount of colorant will be that shown in the above table.

For instance, in the sodium borate system containing a single colorant oxide, the composition ranges are as follows:

Broad Preferred l Comporange, range, Colorant oxide nent percent percent Nickel as the single colorant B203 35-70 40-65 Nag() 10-40 15-30 NiO 2-18 5-18 Iron as the single colorant B205 35-70 40-65 NagO 1040 15-30 l F9203 2-18 5-18 Manganese as the single colorant B203 -70 40-65 NazO 10-40 15-30 2 MnO 1-23 5-23 Cobalt as the single colorant B203 35-70 40-65 N aaO 10-40 15-30 35 C00 2-43 5-43 Zine as the single colorant B203 35-70 40-65 Naz() 10-40 15-30 ZnO 2-43 5-43 Copper as the single colorant B202 35-70 40-65 NazO 10-40 15-30 CuO 2-28 5-28 1 Total iron.' 2 Total manganese.

TABLE I1I(b)--COLORANT-ENRICHED GLASSES (PERCENT BY WEIGHT) BB C C DD EE FF Ingredients:

The above frits were made by melting the following raw batch materials, cooling the melt and quenching on a steel plate.

The resulting ultraviolet-absorbing glasses had the following compositions:

Weight percent Glass 1 with Glass 2 with frit H frit T Ingredients S102.. 71.57 71. 59 A120 1. 73 1. 73 11. 44 1l. 2l l. 02 1. 14 13. 57 13. 42

0. U4 04 06 05 014 S 002 00 82. 8 36. G5 Percent purity 21. 3 24. 9 Dominant wave length in millimicrons 567 482. 0 Percent transmittance at 400 mu (2 mln. thickness) 9. 7 19. 5 Color Yellow-green Blue Ingredients: Percent by weight SiO2 60-75 A1203 0.3-10 CaO 3.5-13 MgO 07 CaO-f-MgO 6-15 Nago 12-18 KZO 0-5 BaO 0-5 Low-silica and silica-free glass frits wherein the chromium content is in the reduced state are produced by utilizing an alkali dichromate as the source 0f chromium, and adding thereto a suicient amount of reducing agent such as carbon, sugar, starch, powdered aluminum, iron scale, sea coal, etc., to convert the hexavalent chromium to trivalent chromium. Combinations of sea coal and iron scale in the frit batch have produced high-chrome frits which, when added to molten dlint glasses, produce an emerald green glass comparable to the accepted standard emerald green.

Two frits having the chromium content in the reduced state are shown in the following examples:

FRIT GLASS COMPOSITION Weight percent The batch ingredients were melted at a temperature of 2000 F. for 1 hour, cooled and fritted. The frits were then added by forehearth addition to a glass having the following composition:

Glasswith Glasswith frit K frit U 70. 94 70. 10 1. 69 l. 69 l0. 95 l0. 98 l. 12 l. 12 13. 53 13. 67 KeO 0.43 0. 43 B 203 0. 88 l. 59 Fe203 (total iron) 0. 26 0.22 C1503 (total chromium) 0. 20 0. 20 Analyzed constituents:

FezO (total iron) O. 234 FeO 0 0028 Cr20s (total chromium) 220 CIE data (10 mm.):

Percent bright-ness 35. 4 28. 8 Percent purity 63. 0 75. 0 Dominant Wave length in millimicrons. 555. 5 556. 0

A typical emerald green glass has 35.0% brightness, 66.0% purity, and a dominant wave length-mu of 555.0.

From the graph in the drawing, the similarity in wave length between a natural emerald green glass and glasses of the foregoing examples made with frits U and K will be readily evident.

Examples V and W in Table III demonstrate how the density of the frits of the invention may vary with composition. Examples X through AA demonstrate how the density of the colorant frit may be adjusted to approximate the density of the soda-lime base glass through the use of' the oxides of zinc, lead and barium.

Exemplary frits BB through FF are sodium borate colorant frit compositions, containing colorants other than chromium that are suitable for coloring soda-lime silica base glasses. These frits are low melting and are readily admixed with the base glass at forehearth temperatures to produce uniformly colored composite glasses.

The use of frits AA through EE is demonstrated by the following examples.

An ordinary colorless soda-lime base glass of the composition:

was melted in an ordinary glass melting furnace according to the method described (see column 9). Frit composition BB (Table III) was added to the base glass at forehearth temperatures in the ratio of 6.7 pounds per ton of base glass. This addition was accomplished 1 1 after the base glass had issued from the melting tank into the forehearth at temperatures in the range of 2300- 2600 F.

The resulting composite glass was yellow in color and had the following composition and properties:

CIE. data (2 mm. thickness):

Percent brightness-74 Percent purity-8 Dominant wavelength-575g Frit composition DD (Table III) was added at the rate of 25.3 pounds of frit per ton of base glass to the colorless soda-lime base glass described (see column 10) by the forehearth method described above. The resulting composite glass was light orange in color and had the following composition and properties:

Percent Si02 71.51 A1203 1.73 CaO 10.96 MgO 0.90 Na20 13.48 K20 0.44 B203 0.70 F5203 MnO 0.25

CIE. data (2 mm. thickness):

Percent brightness- 84 Percent purity-1.5 Dominant wavelength-697;

Frit glass composition FF (Table III) was added to the colorless base glass described (see column 10) by the method described above. The ratio of addition was 32.5 pounds of frit per ton of base glass. The resulting composite glass was blue green in color and had the following composition and properties:

Percent Si02 71.27 A1203 1.72 CaO 10.91 MgO 0.90 Na20 13.50 K20 0.44 B203 0.83 Fe203 0.03 CuO 0.40

CIE. data (2 mm. thickness):

Percent brightness-74 Percent purity-16 Dominant wavelength-486.

While a low-silica-containing, colorant-enriched glass composition, useful in frit or molten form to color a molten base glass has been given above, a preferred composition is as follows:

Ingredients: Percent by weight Si02 18-41 Cf203 R20 31-46 B203 21-37 Total Of R20 and B203 R20 has the same values as given above, and the other oxides, also discussed above with the disclosure of the broad composition, may be present in the same designated amounts.

From the above disclosure, colored glasses meeting the desired optical properties and standards, as recognized by the industry and as set forth in Hagedorn Pat. 3,024,121 and incorporated herein by reference, can readily be made using the apparatus and methods disclosed in the aforesaid patent. Other suitable apparatus and methods are described in U.S. Pat. No. 3,057,175 to R. R. Rough.

Having fully described the invention, what is claimed is:

1. A colorant-enriched glass composition suitable for use in coloring a base glass, said colorant-enriched glass composition consisting essentially of the following ingredients in the indicated percentages by Weight:

Ingredients: Percent by weight Si02 18-41 Cr203 (total chromium) 4-10 R20 31-46 B203 21-37 the total amount of said R20 and B203 being from 52% to 74% by yweight of the glass composition, said R20 being a mixture or' Na20 and K20, said K20 being present in an amount of less than 25% by weight of said Na20.

2. A colorant-enriched glass composition suitable for use in coloring a base glass, said colorant-enriched glass composition consisting essentially of the following ingredients in the indicated percentages by weight:

Ingredients: Percent by weight Si02 l841 Cr203 (total chromium) 4-10 R20 31-46 B203 21-37 the total amount of said R20 and B203 being from 52% to 74% by weight of the glass composition, said R20 being a mixture of Na20 and K20, said K20 being present in an amount of less than 25% by weight of said Na20, and a minor amount of at least one of the following oxides up to the maximum portions indicated:

3. A colorant-enriched glass frit suitable for use in coloring a Ibase glass, said colorant-enriched glass frit consisting essentially of the following ingredients in the indicated percentages by weight:

fPercent by weight Si02 15-50 Cr203 (total chromium) 15-50 R20 23-46 B203 10.5-47 A1203 0.5-7

the total amount of said R20 and B203 being from 44% to 74% by weight of the glass fn't composition, said R20 being a mixture of Na20 and K20, said K20 being present in an amount of less than 25% by weight of said Na20.

4. A colorant-enriched glass frt suitable for use in coloring a base glass, said colorant-enriched glass frit consisting essentially of the following ingredients in the indicated percentages by weight;

References Cited UNITED STATES PATENTS 3,312,556 4/1967 Oikawa et al 106--48 3,285,773 11/1966 Dunning 106--48 3,024,120 3/1962 Babcock 106--52 3,005,721 10/1961 Cerulli 106-47 2,785,091 3/1957 Rex 106-48 2,753,271 7/1956 Treptow 106-48 14 3,203,815 8/ 1965 Michael 106--49 2,923,636 2/1960 Swain. 3,024,121 3/ 1962 Hagedorn. 3,144,270 8/ 1964 Bennett et al 106-48 FOREIGN PATENTS 531,880 10/1956 Canada 1.06-54 OTHER REFERENCES Spriggs et al.: Reaction Kinetics of Porcelain Enamel- Metal Systems, J. Amer. Cer. Soc., vol. 43 (1960), pp. 252-3 TP785A62.

Bancroft et al.. Copper Oxide in the Borax Beads, J. Chem., 34, Pp- 8-11 (1930).

Bancroft et al.: Copper Oxide in the Borax Beads, I. Phys. Chem. 33, pp. 729-30 (1929).

Joos et al.: Das Linienspektrum des Chromoxyds und Die Absorptionsspektren der Chromglser, Z. Physical Chem., 24, pp. 389-392 (1934).

Bancroft et al.: Manganese Oxide in the Borax Bead, I. Phys. Chem., 33, pp. 483-88 (1929).

HELEN M. MCCARTHY, Primary Examiner 

